1. Field of the Invention
The present invention relates to a method of winding a holding sealing material and a method of manufacturing an exhaust gas purifying apparatus.
2. Discussion of the Background
Exhaust gases discharged from internal combustion engines such as diesel engines contain particulate matters (hereinafter, also referred to as PMs), and in recent years, it has become a serious problem that these PMs are harmful to the environment and the human bodies. Exhaust gases also contain toxic gas components such as CO, HC, and NOx, and it has also become a problem that these toxic gas components are harmful to the environment and the human bodies.
In view of these problems, various exhaust gas purifying apparatuses have been proposed as an exhaust gas purifying apparatus which, when connected to an internal combustion engine, collects PMs in exhaust gases and purifies the toxic gas components such as CO, EC, NOx and the like contained in the exhaust gases. Those exhaust gas purifying apparatuses include an exhaust gas treating body made of porous ceramics such as cordierite and silicon carbide; a casing configured to accommodate the exhaust gas treating body therein; and a mat-shaped holding sealing material which contains inorganic fibers and is disposed between the exhaust gas treating body and the casing.
In the exhaust gas purifying apparatus, the holding sealing material holds the exhaust gas treating body by virtue of the elasticity which the inorganic fibers have. Further, the leakage of exhaust gases from a gap between the exhaust gas treating body and the casing is prevented by filling the gap with the holding sealing material.
One known conventional method of manufacturing an exhaust gas purifying apparatus is a method of winding the holding sealing material onto the outer peripheral portion of the exhaust gas treating body, and then press-fitting the exhaust gas treating body with the holding sealing material wound therearound into a casing. Hereinafter, this method will be described in detail with reference to drawings.
FIG. 1A is a perspective view schematically illustrating a conventional method of winding a holding sealing material. FIG. 1B is a perspective view schematically illustrating a conventional method of manufacturing an exhaust gas purifying apparatus which adopts the method of winding a holding sealing material illustrated in FIG. 1A. FIG. 1C is a perspective view schematically illustrating an exhaust gas purifying apparatus manufactured by the conventional method of manufacturing an exhaust gas purifying apparatus illustrated in FIG. 1B.
First, a mat-shaped holding sealing material 210 having a rectangular shape in a plan view is prepared as a holding sealing material. Then, as illustrated in FIG. 1A, the holding sealing material 210 is wound onto the outer peripheral portion of a round pillar-shaped exhaust gas treating body 230 such that side faces 211a and 211b, each including a shorter side (hereinafter, also simply referred to as shorter side face) of the holding sealing material 210, abut on each other. Hereinafter, the exhaust gas treating body 230 with the holding sealing material 210 wound therearound is also referred to as a wound body 240.
Next, as illustrated in FIG. 1B, an exhaust gas purifying apparatus 220 illustrated in FIG. 1C is manufactured by press-fitting the wound body 240 into a casing 250 having an inner diameter slightly shorter than the outer diameter of the wound body 240 (the total length of the diameter of the exhaust gas treating body 230 and the thickness of the holding sealing material 210).
In the exhaust gas purifying apparatus 220 thus manufactured, the holding sealing material 210 is compressed in the casing 250. Therefore, the holding sealing material 210 exerts a restoring force (i.e., a holding force to hold the exhaust gas treating body) to restore the original configuration due to the elasticity which the inorganic fibers have, whereby the exhaust gas treating body 230 is held by the holding sealing material 210.
However, in the exhaust gas purifying apparatus 220 manufactured by the conventional method, there is a problem that side faces 212a and 212b, each including a longer side (hereinafter, also simply referred to as longer side face) and being positioned at each end portion of the exhaust gas purifying apparatus 220, are deformed and thus the holding sealing material 210 is damaged when exhaust gases flow into the exhaust gas treating body.
This problem will be described below in detail with reference to drawings.
FIG. 2 is a cross-sectional view taken along the line E-E of the conventional exhaust gas purifying apparatus illustrated in FIG. 1C.
In FIG. 2, the press-fitting direction of the wound body is indicated by an arrow Y.
As illustrated in FIG. 2, the vicinity of a main face 213b (hereinafter, also simply referred to as second main face) of the holding sealing material 210, which is in contact with the casing 250, is deformed toward the reverse direction of the press-fitting direction. Thereby, at an end portion 220a of the exhaust gas treating body 220 on a side where the exhaust gas treating body is press-fitted, the longer side face 212a is projected from an end face 230a of the exhaust gas treating body 230. Further, at the opposite end portion 220b of the exhaust gas treating body 220, the longer side face 212b is depressed below an end face 230b of the exhaust gas treating body 230.
The reason for this is that when the wound body 240 is press-fitted into the casing 250, a shear force is applied between a main face 213a (hereinafter, also simply referred to as first main face) of the holding sealing material 210, which is in contact with the exhaust gas treating body 230, and the second main face 213b. This sheer force shifts the second main face 213b off the position of the first main face 213a to deform the holding sealing material.
As described above, at the end portions 220a, 220b of the exhaust gas purifying apparatus 220, the longer side faces 212a, 212b of the holding sealing material 210 are not substantially parallel to the end faces 230a, 230b of the exhaust gas treating body 230, and thus the longer side faces 212a, 212b are inclined relative to the end faces 230a, 230b. 
The term “substantially parallel” used herein means that the longer side face of the holding sealing material is parallel to the end face of the exhaust gas treating body or that the longer side face is inclined relative to the end face to an extent that its inclination is effectively negligible.
Moreover, when exhaust gases flow into the exhaust gas treating body in a state where an end face of the wound body 240 is inclined, an area of contact between the longer side faces 212a, 212b and the exhaust gases is increased and therefore the longer side faces 212a, 212b are vulnerable to wind erosion caused by the flowing exhaust gases. The holding sealing material 210 may sometimes be damaged due to development of such wind erosion occurring in the longer side faces 212a, 212b. 
This leads to a problem that the exhaust gases are leaked from a gap generated due to the wind erosion, or in some cases, the exhaust gas treating body 230 comes off because the exhaust gas treating body 230 cannot be sufficiently maintained when the holding sealing material 210 is damaged.
In view of these problems, Japanese Patent Application Publication (KOKAI) No. 2007-092553 for example discloses a method of winding a holding sealing material and a method of manufacturing an exhaust gas purifying apparatus, which use a holding sealing material with an inclined longer side face.
The contents of Japanese Patent Application Publication (KOKAI) No. 2007-092553 are incorporated herein by reference in their entirety.